A ball check valve has a ball which should block the flow of fluid when the flow becomes excessive due to an external leak or other event downstream from the valve. For example, a sight glass may break. It is desired to stop the leak because the fluid may be hazardous, expensive or for cleanliness generally.
The ball check is normally in a resting position that permits free flow of fluid. If there is excessive flow, the ball check has to be moved to a seated position that should block the flow. The ball should move from the resting position to the blocking position at a situation of excess flow. When the ball is in the blocking position, the inlet pressure maintains the ball check in that position.
Currently known ball check valves are susceptible to leakage, breakage and jamming after repeated use. Ball check valves can also be unreliable in operation, particularly for certain fluids such as petroleum. There may be a buildup on interior surfaces of the valve or a contaminant can become lodged between an interior surface and the ball. In severe cases, the valve may become inoperative due to the ball check not seating properly, allowing fluid to flow past the ball check.
A specific example of an inadequate prior art ball check valve is shown in FIG. 17. It is a sleevable/plug type where a valve plug is inserted into a unitary body. The valve plug is tapered, with distinct sides. The position the check ball is supposed to be in when blocking the flow of fluid (shown in dashed outline) is easily impeded. The prior art valve uses an upward projection, which is susceptible to bending or even breaking, and may be difficult or expensive to manufacture. As a metal pin, tapered and pressed into a taper hole in the plug, there is no seal and the valve can have minor leakage.